Control Strategies and Evaluation of Modular Dual-Active Bridge for DC Collector Grid in Offshore Wind Parks

A modular three-phase dual-active bridge (DAB3) is a promising candidate for a two-stage dc collector grid in offshore wind parks. This paper aims to develop controllers of the modular DAB3 in input-parallel-output-series (IPOS) system with the capability to regulate input voltage, share input current coming from wind turbines, and distribute output voltages evenly among power converter modules. Performance analyses are performed under identical and nonidentical submodules. Simulation results show that the proposed controllers successfully distribute the input current and output voltages uniformly. In addition to them, the current oscillation can be avoided even under the input voltage control mode by implementing the instantaneous current control.